code: def unpack_batch(
      batch: Sequence[Sequence], ignore_fields, input_fields
  ):
      return {"_single": batch}
  
file_path: fastNLP/fastNLP/core/collators/packer_unpacker.py
imports: from collections import defaultdict
  from functools import reduce
  from typing import Sequence, Mapping, Dict
label_desc: Use image node_id 1 for calling the SinglePackerUnpacker obj's underlying member method code with example usage: obj.unpack_batch(batch, ignore_fields, input_fields) and returns: dict